The present disclosure relates generally to aspiration systems used in phacoemulsification procedures, and more particularly, to aspiration systems employing quick-opening vent valves to improve operation.
Typical surgical instruments suitable for phacoemulsification procedures on cataractous lenses include an ultrasonically driven phacoemulsification hand piece with a cutting needle and an irrigation sleeve, and a control console. The hand piece is attached to the control console by an electric cable and flexible tubing. The flexible tubing supplies irrigation fluid to the surgical site and carries aspiration fluid from the surgical site to a waste or discard reservoir.
During a phacoemulsification procedure, the tip of the cutting needle and the end of the irrigation sleeve are inserted into the anterior segment of the eye through a small incision in the eye's outer tissue. The surgeon brings the tip of the cutting needle into contact with the lens of the eye, so that the vibrating tip fragments the lens. The resulting fragments are aspirated out of the eye through the interior bore of the cutting needle, along with irrigation fluid provided to the eye during the procedure.
Throughout the procedure, irrigating fluid is infused into the eye, passing between the irrigation sleeve and the cutting needle and exiting into the eye at the tip of the irrigation sleeve and/or from one or more ports or openings formed into the irrigation sleeve near its end. This irrigating fluid is critical, as it prevents collapse of the eye during the removal of the emulsified lens, protects the eye tissue from the heat generated by the vibrating of the ultrasonic cutting needle, and suspends the fragments of the emulsified lens for aspiration from the eye.
During the surgical procedure, the console controls irrigation flow rates and aspiration flow rates to maintain a proper intra-ocular chamber pressure balance in an effort to maintain a relatively consistent fluid pressure at the surgical site in the eye.
Aspiration flow rates of fluid from the eye are typically regulated by an aspiration pump that creates a vacuum in the aspiration line. The aspiration flow and/or vacuum are set to achieve the desired working effect for the lens removal. While a consistent fluid pressure in the eye is desirable during the phacoemulsification procedure, common occurrences or complications create fluctuations or abrupt changes in fluid flow and pressure at the eye. Occlusion break surge is an undesirable shallowing of the anterior chamber of the eye that results when vacuum is generated within the aspiration pathway due to a flow obstruction and then that obstruction is suddenly removed. This results in a high demand for fluid from the eye to relieve the vacuum, causing a sudden shallowing of the anterior chamber.
The problem of occlusion surge has been addressed in the past in a number of ways including adding a reduced cross-section orifice in the aspiration line. While such a reduced area reduces the effects of occlusion surge, reduction of aspiration path cross-section can also increase the potential for clogging during the procedure. Other methods have been used or proposed that involve torturous paths, with corners, angles, and fluid restrictors that are also subject to clogging. Some prior solutions involve a resistive element at or near the pump. However, the effectiveness of these solutions is limited due to the relatively large tubing compliance between the resistive element and the eye. Another attempted solution has been the use of increased lengths of flexible aspiration tubing in an attempt to increase overall tubing resistance. This solution of adding flexible tubing length has the undesirable effect of adding additional compliance to the aspiration path. The additional compliance increases the demand for fluid from the eye during occlusion break, sometimes entirely offsetting the benefits obtained by the longer tubing length.
Therefore, there remains a need for an improved system for reducing occlusion surge that that can occur during a medical procedure. The present disclosure is directed to addressing one or more of the deficiencies in the prior art.